After 1492 the world became a very different place. Western Europe's "discovery" of and imperial thrust into the equally old world of the Americas set in rapid motion the final stages of the human and biological exposure of the earth's constituent parts to each other and the tying of those parts together with nautical lines.
Before Columbus, various ancient worlds -- Africa, Asia, Europe, and the Americas -- lay largely isolated from each other, shrouded in tantalizing mystery or blissful ignorance. Asians knew parts of Africa and even Europe (and the Chinese at least had the technology and knowledge to exploit both), but chose largely to stay home. North Africans certainly knew Europe and had colonized the Iberian peninsula for nearly eight centuries. But Western Europeans, driven by economic forces, social restlessness, and an evangelical religion, did the most to systematically intrude themselves and their ways of life into the known, inhabited parts of the world. Save for a few readers of ancient Norse sagas, no one knew of the Americas, and the Americans knew nothing of the rest of the world.
In 1492 Cristoforo Colombo, a Genoese sailor in the